Not Applicable.
1. Field of the Invention
The present invention relates generally to head stack assemblies, and more particularly to a head stack assembly having an actuation linkage for moving a load beam and attached head.
2. Description of the Prior Art
A typical disk drive includes several disks having tracks with the disks stacked upon one another, a disk controller for generating a servo control signal, a disk drive base, and a head stack assembly attached to the disk drive base. The head stack assembly includes a body portion having a bore. The bore defines a pivot axis. The head stack assembly further includes several actuator arm bodies which extend from the body portion. Each of the actuator arm bodies generally define a longitudinal axis and are configured perpendicular to the pivot axis. Each of the actuator arm bodies is provided with load beam, sometimes a pair of load beams, which extends from it along the longitudinal axis. Suspended distally from each load beam is a head. The body portion and the actuator arm bodies are configured to rotate about the pivot axis in response to the generated servo control signals from the disk controller that actuates a voice coil motor. In so doing, the attached load beams and heads to move relative to the tracks disposed upon the disks. Thus the servo control signals are used for selectively positioning the heads over respective tracks.
There have been prior art attempts to modify the head stack assembly design to refine the controlled positioning of the heads in relation to respective tracks. Such designs have been referred to as implementing dual or second stage actuation. In this context, primary actuation refers to the servo controlled rotational movement of the actuator arm bodies about the pivot as actuated by the voice coil motor.
Second stage actuation offers increased positioning control of the head relative to a given track, which in turn results in the ability to more tightly space the tracks, and therefore resulting in the benefit of the disks having an increased data density.
In a prior art design, for example, the load beam may be modified so as to be of a two-piece construction. A distal portion of the load beam may be controlled to move relative to the rest of the load beam for moving the attached head. An actuator is attached to the load beam for providing the force required to move the distal portion of the load beam. Some current designs implement two actuators for each load beam. Such actuators may be formed of a piezo-electric material. In this regard, the actuator controlled movement of the distal portion of the load beam is considered to be a second stage actuation of the movement of the attached head.
However, assembly considerations regarding the actuator on such two-piece load beam present many technical difficulties. Such a prior art design requires the burden of attachment of an actuator to each load beam. Attachment of such actuator to the load beam results in a subassembly which is a relatively fragile part. In this regard, further handling of such subassembly requires special care. Further, such subassembly must typically undergo a testing process, the failure of which results in loss of an expensive part. Next, the actuator/load beam/head subassembly must be physically attached to and electrically connected with an actuator arm body. As the actuator/load beam/head subassembly is relatively fragile, the actuator arm body physical attachment and electrical connection processes must be taken with special care. The resulting subassembly must typically undergo a testing process, the failure of which results in loss of an expensive part. Finally, where a resulting head stack assembly includes an array of closely spaced actuator arm bodies, such head stack assembly must be specially handled so as to protect the actuators from damage during shipment.
Other prior art second stage actuation designs include micro-actuation at the head level. This results in the various problems as discussed above with respect to actuators mounted at the load beam level, as well as additional other difficulties.
Accordingly, there is a need in the art for an improved head stack assembly implementing a second stage actuation in comparison to the prior art.
An aspect of the invention can be regarded as a head stack assembly for use in a disk drive. The head stack assembly includes a body portion having a bore. The bore defines a pivot axis. The head stack assembly further includes at least one actuator arm body extending from the body portion and defining a longitudinal axis. The at least one actuator arm body is sized and configured to rotate about the pivot axis disposed perpendicular to the longitudinal axis. The head stack assembly further includes at least one load beam extending from the at least one actuator arm body along the longitudinal axis. The head stack assembly further includes a head connected to the at least one load beam. The head stack assembly further includes a linear actuator connected to the body portion. The linear actuator is sized and configured to selectively expand and contract. The head stack assembly further includes at least one actuation linkage connected with and interposed between the at least one actuator arm body and the at least one load beam. The at least one actuation linkage is further connected to the linear actuator. Selective expansion/contraction of the linear actuator moves the at least one actuation linkage which moves the connected at least one load beam and the connected head with a transverse component relative to the longitudinal axis of the associated at least one actuator arm body.
In an embodiment of the present invention, the at least one actuation linkage includes a distal member connected with an intermediate member. The distal member is distally connected to the at least one actuator arm body and the at least one load beam. The intermediate member is connected to the linear actuator and extends along the at least one actuator arm body. The at least one actuation linkage may include an actuation linkage hinge interposed between and attached to the distal member and the intermediate member. The at least one actuation linkage may include a distal member hinge interposed between and attached to the distal member and the at least one actuator arm body. The at least one actuation linkage may further include an intermediate member hinge interposed between and attached to the intermediate member and the at least one actuator arm body. It is contemplated that at least one actuator arm body may include a plurality of actuator arm bodies. In this regard, the at least one load beam includes a plurality of load beams associated with respective ones of the plurality of actuator arm bodies, and the at least one actuation linkage includes a plurality of actuation linkages associated with respective ones of the plurality of actuator arm bodies and the plurality of load beams. Preferably, the linear actuator is a piezoelectric element. Further, the body portion may include a shoulder, and the linear actuator may be attached to the shoulder.
In addition, according to another aspect of the present invention, there is provided a disk drive which includes the above described head stack assembly.